This invention relates to a landing approach system and more particularly to a mobile based landing system.
In controlling air traffic at installations of relatively small areas, the controller operator must be able to identify, position fix, and vector cooperative or friendly aircraft. Although GCA systems perform such functions, such GCA systems are very expensive and are mainly restricted to relatively large operations because of their weight, size, and power consumption. Since mobile air control requirements may range from very small facilities, where only 1 or 2 aircraft may be involved, to facilities where larger numbers of aircraft have to be controlled simultaneously, such control landing systems must comprise equipment which is small in size, lightweight, consumes little power and is relatively cheap to manufacture and maintain. In developing such lightweight portable landing systems, it was found that L-band transponder systems normally available in commercial and military aircraft could be included as one component of the system. Such L-band transponder systems, in addition to providing an identification signal in response to the ground station interrogation, also provide automatic encoded altitude information to the ground or controlling station. The automatic altitude encoding is usually referred to as Mode C operation on the aircraft L-band transponder.